Orgasm without erection

For a few years now, I have been having premature ejaculation, sometimes even without achieving an erection....limp ejaculation. I have tried viagra, but still does not solve the premature ejaculation super sensivitity. Only after the ejaculation that the erection somewhat happens. It is a very frustrating phenomena that I am having. Whether it be masturbation or getting sex, the same phenomena deprives me from having good sex. Abstinence makes things worse. The supersensivity turns to hyper sensitivity, in that ejeculation happens without penetration and a limp erection. Anyone going through something simlar and how can I solve this problem ? I am over 50.